Color stabilization of fatty-acid forerunnings



United States Patent O Int. oi. c11c 1/10 U.S. Cl. 260-419 10 Claims ABSTRACT OF THE DISCLOSURE Discoloration and subsequent darkening of fatty-acid forerunnings are prevented by heating the fatty acids with at least one alkyl ester of titanic acid and/or polytitanic acid at a temperature of approximately 180-250 C., and then distilling the resultant mixture to recover the fatty acids. The heating step is carried out for about .5-4 hours.

BACKGROUND OF THE INVENTION This invention relates to a process for preventing the discoloration and subsequent darkening of fatty-acid forerunnings obtained during the distillation of fatty acids from hydrolyzed acid oil obtained by splitting of soap stock or hydrolysis of coconut oil and palm nut oil under pressure. More particularly, the invention relates to the discovery that distilled fatty acids treated with certain compounds have a color-stabilizing influence on fattyacid forerunnings of the type described above.

The state of the art can be seen from a consideration of US. Pat. 2,862,943 and from German DAS 1,214,212. Inorganic and organic compounds have been conventionally employed in the art for preventing discoloration. However, as discussed in said German publication, these conventional processes have many disadvantages. When using the organic and inorganic compounds of boric acid,

unsaponifiable condensation products of the fatty acids are obtained in the distillation residue. In fact, the production of exactly these condensation products from fatty acids is described in DAS 1,073,665, wherein oxygencontaining boron compounds are employed as condensa tion catalysts. The yield of unsaponifiable condensation products, in accordance with this process, is up to 92%. U.S. Pat. 2,583,028 and British Pat. 1,081,522 describe the treatment of fatty acids with boron trifiuoride or with the ether complex thereof. However, extremely grave corrosion problems are encountered in these processes.

One of the objects of the present invention is to provide a process for preventing the discoloration and subsequent darkening of fatty-acid forerunnings.

Another object of the present invention is to provide a novel process for purifying fatty acids and for preventing the formation of unsaponifiable compounds therein which overcomes the disadvantages and deficiencies of the prior art methods.

A further object of the invention is to provide fatty acids of improved color, even when using low grade substances as starting materials.

These and other objects and advantages of the present invention will become apparent to those skilled in the art from a consideration of the following specification and claims.

SUMMARY OF THE INVENTION In accordance with the present invention, it has been found that the discoloration and subsequent darkening of the first or forerunnings of fatty acids having 8-12 carbon atoms can be prevented by heating the fatty acids with about 0.2-1% by weight, preferably 0.4-0*.6% by weight, based on the amount of fatty acid employed, of an alkyl ester of titanic acid, polytitanic acid or a mixture thereof. The heating step is conducted for approximately 0.5-4 hours, preferably 1-3 hours, to temperatures of about 180-250 C., preferably 200230 C., under normal pressure. A weak vacuum may be employed. Subsequently, the fatty acid is distilled.

Substances such as the alkyl esters of titanic acid or of the polytitanic acids are known to be interesterification and esterification catalysts having an excellent effectiveness. However, the color-stabilizing influence of such compounds on fatty-acid forerunnings has not been described heretofore.

The fatty-acid forerunnings treated in accordance with the present invention are obtained as the first runnings or heads during the distillation of fatty acids from the hydrolysis of coconut oil or palm nut oil. The neutralization of the free fatty acids in crude coconut oil and palm nut oil with alkali results in the formation of soap. The separated soap solution is known as soap stock, which contains some neutral oil. It is hydrolyzed or split by acidulation with mineral acids which causes a separation of the fatty acids along with the neutral oil. This mixture of fatty matters is known as acid oil. This acid oil is hydrolyzed, and the fatty acids obtained by distillation have an inferior color quality as compared with fatty acids obtained by the direct hydrolysis of coconut or palm nut oil. Also, a distinction should be made between the fatty acids from hydrolyzed acid oil obtained by splitting of soap stock during the refining of coconut oil or palm nut oil, and fatty acids from the pressure-hydrolysis of coconut oil or palm nut oil. The fatty acids from hydrolyzed acid oil obtained by splitting of soap stock exhibit a poorer color quality than the fatty acids obtained by direct hydrolysis of coconut oil or palm nut oil and tend to exhibit discoloration and subsequent darkening to an even greater extent than the latter. The process of the present invention, however, makes it possible to also produce color-stable distillates from the fatty acids from hydrolyzed acid oil obtained by splitting of soap stock during the refining of coconut oil and palm nut oil.

The color stability of the fatty-acid forerunnings treated in accordance with the invention as well as that of the untreated materials was determined by heating the samples in a small glass tube having a diameter of 14 millimeters and a filling height of 115 millimeters to 200 C. during a pen'od of 6 hours. This heating test was conducted in a thermostatically controlled oven which was not opened during the entire duration of the test. The test tubes were each covered with a cap.

The color intensity was measured in iodine color number units, wherein the iodine color number indicates how many milligrams of free iodine are contained in milliliters of aqueous iodine-potassium iodide solution at the same depth of color, when measured at a layer thickness of 25 millimeters.

The process according to the present invention can be conducted batch-wise as well as continuously.

The following examples are given merely as illustrative of the present invention and are not to be considered as limiting. Unless otherwise noted, the percentages therein and throughout the application are by weight.

EXAMPLES OF THE INVENTION Example 1 (a) The untreated fatty-acid forerunnings employed, derived from the hydrolysis of acid oil obtained during refining, exhibited the following composition, in accordance with gas chromatographic analysis (data in percent by weight): C -acid: 0.5; C -acid: 58.2; C -acid: 28.5; C -acid: 10.1; C -acid: 1.8; C -acid: 0.6; and 0.3% each of methyl heptyl and methyl nonyl ketones. 3,000 parts by weight of said fatty-acid forerunnings containing about 2% of water, were dehydrated under agitation and mixed, at a sump temperature of 220 C., with 0.5% by weight of butyl titanate. The treatment time was 2.5 hours. During this period, a temperature of 220 C. was maintained. Thereupon, the sump temperature was lowered to 90 C. by cooling, and the contents of the flask were distilled over a distillation column under a vacuum of 1-2 torr within about 2 hours. Three fractions were withdrawn.

As fraction I, 7.8% by weight was obtained; as fraction II, 81.2% by weight, and as fraction III, 5.1% by weight, based on the amount of anhydrous fatty-acid forerunm'ngs employed. The amount of residue was 5.9% by weight. The values obtained are set forth in Table I.

(b) For comparison purposes, 3,000 parts by weight of untreated fatty-acid forerunnings were distilled under the same conditions, the resultant data also being recited in Table 1.

Example 2 (a) 3,000 parts by weight of fatty-acid forerunningsfrom the pressure dissociation of coconut oil and palm nut oil were dehydrated at 450 torr and mixed with 0.6% by weight of the ethyl ester of polytitanic acid at a sump temperature of 210 C. During the treatment time of 3 hours, a temperature of 220 C. was maintained. Thereafter, the sump temperature was lowered by cooling to 90 C., and the contents of the flask were distilled under a vacuum of 1-2 torr over a distillation column within about 2 hours. As fraction I, 7.2% by weight was obtained; as fraction II, 81.5% by weight; as fraction III, 6.1% by weight. The residue was 5.2% by weight.

(b) For comparison purposes, 3,000 parts by weight of untreated fatty-acid forerunnings from the pressurehydrolysis of coconut oil and palm nut oil were distilled under the same conditions. The values are indicated in Table I.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included herein.

We claim:

1. A process for preventing the discoloration and subsequent darkening of fatty-acid forerunnings having from 8 to 12 carbon atoms which comprises heating the fatty acids with at least one alkyl ester of an acid selected from the group consisting of titanic acid and polytitanic acid at a temperature of approximately 180250 C., and then distilling the resultant mixture to recover the fatty acids.

2. The process of claim 1, wherein 0.24% by weight of said alkyl ester of titanic acid or polytitanic acid or a mixture thereof is added to said fatty-acid forerun-nings.

3. The process of claim 1, wherein the alkyl ester additive is heated with said fatty-acid forerunnings for about 0.5-4 hours.

4. A process for preventing the discoloration and subsequent darkening of fatty-acid forerunnings having from 8 to 12 carbon atoms which comprises heating the fatty acids with about 0.21% by weight of an alkyl ester of titanic acid or polytitanic acid or a mixture thereof for approximately 0.5-4 hours at a temperature of about 180250 C., and then distilling the resultant mixture to recover the fatty acids.

5. The process of claim 4, wherein 0.40.6% by weight of said alkyl ester is added to said fatty-acid forerunnings.

6. The process of claim 4, wherein heating is carried out for 13 hours.

7. The process of claim 4, wherein the mixture of fattyacid forerunnings and alkyl is heated at ZOO-230 C.

8. The process of claim 4, wherein th mixture of fattyacid forerunnings and alkyl ester is heated under a weak vacuum.

9. The process of claim 4, wherein said process is conducted continuously.

10. The process of claim 4, wherein the alkyl groups in said alkyl ester have from 1 to 4 carbon atoms.

TABLE I Fraction I Fraction II Fraction III Iodine Iodine Iodine Color Color Color No. No. No. Amount, Iodine afterfi Amount, Iodine atterfi Amount, Iodine aiterfi percent by Acid Color hours at percent by Acid Color hours at percent by Acld Color hgurs Example weight No. No. 200 0. weight No. No 200 C. weight No No 200 C. 1 a 7.8 381 1 28. 5 81.2 368 1 7.8 5.1 305 1.2 24 100 7.0 382 5.4 108 81.3 367 2.1 52 5.2 307 2.6 52 2(a) 7. 5 365 1 16. 3 s1. 4 358 1 5. 3 5. 6 295 1.1 14 2(1)) 7.8 366 2.2 33 81.1 359 1.1 20 5.2 294 1.0 20

The alkyl esters shown in the examples are merely References Cited exemplary of the additives which may be employed 111 UNITED STATES PATENTS accordance with the invention. Generally, the alky r a1 et al 260-412 groups in sa1d alkyl esters have from 1 to 4 carbon 2,171,202 8/1939 U b n i6 7, atoms (usually designated as lower alkyl and 1nclude 60 LEWIS GOTTSPrimary Examiner groups such as methyl, ethyl, n-propyl, isopropyl, nbutyl, isobutyl, sec-butyl and tert-butyl.

E. G. LOVE, Assistant Examiner 

